HIV cannot be completely ruled out even after 5 weeks of testing, because the window period for HIV is determined by the test method. Some testing methods have a relatively long window period, and HIV can only be ruled out if the antibody is still negative after 3 months of retesting. 2-12 weeks after HIV infection, about 42 days on average, can be detected in the blood. This is only a preliminary test, and the final determination will be made 3 months later.